Method of outgassing and purifying electrically conductive bodies



y 1936 H. E. MENDENHALL 9,fi55

METHOD OF OUTGASSING AND PURIFYING ELECTRICALLY CONDUGTIVE BODIES Filed Oct. 20, 1934 HIGH POTENTIAL SOURCE FIG. 2

l/WE/WDR H. E. MENDf/WMLL Wm 6M ATTORNEY Patented May 5, 1936 UNITED STATES- PATENT OFFICE METHOD OF OUTGASSING- AND PURIFYING" ELECTRICALLY CONDUCTIVE BODIES Hallam E;.Mendenhall, Summit, N. J assignor. to,

Bell Telephone Laboratories,

Incorporated,

' New York, N. Y'.,.a' corporation of New York Application October 20, 1934, Serial:No. 749,'319

' 2 Claims; (01. 250-275) I Thisinvention relatestotmethods'of outgassing and purifying electrically conductive bodies and more particularly to thefabrication. and outgas sing of GIBCtIOdGSlfOI' electrondischarge devices.

; produced conveniently by machining graphite blocks to. the desired configuration and size.. It has been found, however, that asaresult of" such machining, the electrodes-have thereon a.quantity of minute loose graphite particles which can notbe removed effectively by mechanical processes In the operation of an electron discharge device including electrodes thus produced, the.

loose graphite particles are activated: by the potentials extant betweenthe electrodesof the device and forman objectionable coating. upon.

other electrodes. For example,.the particlesmay form a non-emitting coating uponlthea cathode of. the device and thereby. seriously impair the operation thereof.

Furthermore, graphite. electrodes: constitute black body radiators and hence must be heated: to very high temperatures'to remove occluded gases therefrom. If it were. attempted to heat such electrodes to the necessary temperature within a vitreous enclosing vessel. by a high frequency electromagnetic field, the enclosing vessel would become excessively heated and might collapse or give off water vapor which" would deleteriously: affect other electrodes, particularly the electron emitting cathode.

In accordance: with this invention, these. difficulties are overcome andigraphitgelectrodes substantially free of occluded. gases,iloose graphite particles. and. other foreignmatt'er are produced.

In order to remove the graphite particles and other foreign matter, a high poential is impressed between the electrode and an electrical conductor enclosed in an insulating member disposed in proximity to the electrode. Under the influence of this potential the graphite particles and other foreign matter are released from the electrode and deposited upon the insulating member.

The electrode thus treated may then be mounted in proper position within the enclosing vessel of an electron discharge device and subjected to a high frequency field which may be produced by a coil encompassing the enclosing vessel. In order to enable heating of the electrode to a degree sufficient to remove occluded gases substantially completely therefrom without unduly heating the enclosing, vessel, a cooling: jacket is-providedxabout the enclosing vessel, the jacket. beingv encompassed by the high frequency coil.

The invention and the manner of practicing: it will be understood more clearly and fully from: 5,. the following detailed description with reference to the accompanying; drawing. in which:

Fig. 1 shows one embodiment of: the invention, in a perspective view partly in cross-section ofan. electrode and apparatus: associated therewith 101' for: removing foreign matter' from; the electrode; and

Fig. 2 is. an elevational view partly in; cross- 7 section of an electron discharge; deviceandv ap=-- paratus associated therewith for; outgassing an. 15.

electrode of the device in: accordance with: this:

invention.

Referring now to thedrawingotherei is; shown in- Fig. 1- an electrode including ahollow rectangular body, l provided with oppositely disposed flange portions H having longitudinal bores [2- there,- through forv receiving supports-for the electrode. The electrode may be utilized as the anode of' an; electron discharge device and may be ma-- chined in one piece from a block of graphite. 5:

a result of the machining process, the inner and outer surfaces of. the electrode have thereon; minute: particles of graphite and also other foreign matter which cannot be removed expeditiously by mechanical processes. eration of an electron discharge devicein which the electrodemay be incorporated. theseparticles are activated by the potentials extant between-the electrodes of the device and. may deposit upon a cathode and form a. black non-emitting. coating. 35.

thereon which would seriously impair the operation ofthe device.

In accordance with: this invention, graphiteparticles and-other; foreign matter uponthesurfaces of the electrode are removed therefrom by 40 impressing a high potential, which may be obtained from a suitable source 3 and may be constant or high frequency, between the electrode and a conductor M. The conductor I 4 may be a continuous wire forming a closed loop as shown, which is threaded through a plurality of insulating members I5, such as glass tubes, disposed within the body portion ID of the electrode and in proximity to the inner surface thereof. The insulating members serve as a barrier between the wire loop and the graphite anode to prevent the establishment of an are which would produce pitting or puncturing of the anode. Preferably the insulating members or glass tubes l5 extend beyond the ends of the body portion l 0.

During; the, op 3m posited upon the insulating members or glass tubes l5.

Although the insulating members or glass tubes 15 are shown within the body I0 of the electrode in Fig. 1, it will be understood, of course, that they may be disposed in proximity to the outer surfaces of the electrode if itis desired to remove graphite particles and other foreign matter from the outer surfaces more completely.

After the electrode'has been treated as above described, the insulating membersror glass tubes I5 may be removed and the electrode mounted in proper position within an enclosing vessel "3 of an electron discharge device as shown in Fig. 2.

For example, it'may be supported from a stem ll ,of the enclosing vessel l6 by a plurality of supports or rods 18 extending from a collar 36 secured about the stem l1 and entering the bores l2 in the flanges l I. The electrode or anode may encompass a filamentary cathode I9 also supported from the stem l1.

7 The enclosing vessel I6 is disposed Within and spaced from the inner walls of a jacket 20, which may be of a glass having high heat resisting qualities, the jacket 20 being provided at one iend with an inlet 2i and at'the other end with an outlet 22. Suitable hose connections 23 and 24 are coupled to the inlet and outlet, respectively for associating the jacket with a fluid circulating system. The jacket 20 is sealed at its upper 'end by a resilient closure member 25 in which one end of the enclosing vessel I6 is fitted and held. The enclosing vessel US may beheld in proper position within the jacket 20 by a metallic hook member-.26 carried by the hose 23 and engaging a metallic hook member 21 sealed in one end of the enclosing vessel IS. The hook member 21 may serve as a leading-in conductor for a grid electrode, not shown, so that suitable potentials may be applied to the grid electrode 5. during the evacuation treatment of .thedevice.

The jacket 20 is encompassed by a coil 29, through which a high frequency current may be passed, the coil being positioned to encompass the anode l0 and substantially coextensive therewith. The coil 29 may comprise a plurality of ribbon-like turns insulated from each other and held in spaced relation by a rod 30 carrying insulating spacers 3|. One end of the coil 29 may be electrically connected to a metallic support 32 and the other end may be connected to a conductor 33.

In the fabrication of the electron discharge device, the enclosing vessel I 6 is coupled by a tubulature 34 to a header 35 constituting a part of the evacuating system. The cathode l9 and the grid may be denuded of occluded gases in a manner well-known in the art. By passing high frequency current through the coil 29, high frequency current will be induced in the anode, thereby degassing it by the heating effect. Inasmuch as the anode, if of graphite, constitutes a black body radiator, it will be appreciated that it must be heated to a very high temperature to efiectively denude it of occluded gases. Such a temperature may be reached, of course, by passing a current of suflicient magnitude through the coil 29. However, because of the high radiating properties of the anode, the enclosing vessel Hi may become heated to an excessively high temperature so that it may give off water vapor, which would deleteriously affect the cathode and grid, or the glass vessel may collapse. In accordance with this invention, these disadvantages are overcome and theheating of the anode to a sufficiently high temperature is made possible by passing a cooling fluid through the .jacket '20 during the outgassing treatment of the anode.

The cooling fluid maintains the enclosing vessel at a safe temperature irrespective of the degree to which the anode may be heated. During the heating of the anode the gases released may be removed from the enclosing vessel 16 by the evacuating system, and at the desired time in the evacuation process the tubulature 34 may be sealed and disconnected from the header 35.

Although the invention has been described with.

this invention as defined in the appended claims..

What is claimed is:

1. The method of treating a hollow graphite anode for electron discharge devices which comprises disposing a plurality of insulating tubes having electrical conductors therein within said anode, and applying a high potential between said anode and said conductors.

2. The method of treating a hollow graphite anode of the machined type which comprises placing an insulating tube within said anode, threading a conductor through the tube, connecting the ends thereof to forma loop, and establishing an electrostatic field of high potential between the loop and said anode, whereby residue particles of graphite and foreign matter are liberated from the surface of said anode and deposited on said insulating tube. 

